Many vehicles having a hydrostatic transmission also have an underspeed actuator as a component of a control assembly which controls the speed and direction of travel of the vehicle. With some underspeed actuators, proper operation of the control assembly is dependent upon accurate positioning of an input shaft, which extends through the wall of the transmission case, relative to the linear pathway that a pivot shaft of the underspeed actuator takes during operation of the control assembly. The input shaft provides an input signal to the control assembly and when the shafts are misaligned, a false speed signal is transmitted to the pump controls, particularly at the full underspeed condition. One of the problems encountered with such control assemblies is that, heretofore, the underspeed actuator has been mounted to one wall of the transmission case separately from and independently of the mounting of the input shaft. Thus, due to manufacturing tolerances, the control assembly was occasionally assembled with the input shaft and pivot shaft in a misaligned condition. Also, vibrations in the transmission case can cause underspeed actuator to move relative to the input shaft, thereby causing a false speed signal to be transmitted to the pump.